Clinical Pharmacology for Aponvie
Mechanism Of Action
Aprepitant is a selective high-affinity antagonist of human substance P/neurokinin 1 (NK1) receptors. Aprepitant has little or no affinity for serotonin (5-HT3), dopamine, and corticosteroid receptors, the targets of existing therapies for postoperative nausea and vomiting (PONV).
Aprepitant has been shown in animal models to inhibit emesis via central actions. Animal and human Positron Emission Tomography (PET) studies with aprepitant have shown that it crosses the blood brain barrier and occupies brain NK1 receptors.
Pharmacodynamics
NK1 Receptor Occupancy
In two single-blind, multiple-dose, randomized, and placebo-controlled studies, healthy young men received oral aprepitant doses of 10 mg (N=2), 30 mg (N=3), 100 mg (N=3), or 300 mg (N=5) once daily (0.08, 0.24, 0.8, and 2.4 times a single 125 mg dose of oral aprepitant, respectively) for 14 days with 2 or 3 subjects on placebo. Both plasma aprepitant concentration and NK1 receptor occupancy in the corpus striatum by PET were evaluated, at predose and 24 hours after the last dose. At aprepitant plasma concentrations of approximately 10 ng/mL and 100 ng/mL, the NK1 receptor occupancies were approximately 50% and 90%, respectively. The oral aprepitant regimen produced mean trough plasma aprepitant concentrations greater than 500 ng/mL in adults, which would be expected to, based on the fitted curve with the Hill equation, result in greater than 95% brain NK1 receptor occupancy. However, the receptor occupancy for the PONV dosing regimen has not been determined. In addition, the relationship between NK1 receptor occupancy and the clinical efficacy of aprepitant has not been established.
Cardiac Electrophysiology
In a randomized, double-blind, positive-controlled, thorough QTc study, a single 200 mg intravenous dose of fosaprepitant, a prodrug of aprepitant, had no effect on the QTc interval. QT prolongation with the recommended APONVIE dosing regimen is not expected.
Pharmacokinetics
Absorption
Following administration of a single intravenous 32 mg dose of APONVIE administered as a 30 second injection to healthy subjects, mean (CV%) area under the plasma concentration-time curve (AUC0-∞) was 7.8 (27.4%) mcg·hr/mL and mean plasma concentration at 5 minutes postdose was 2.1 (19%) mcg/mL.
In healthy subjects, a single dose of 32 mg of APONVIE administered as a 30 second intravenous injection resulted in a 13% higher AUC0-∞ of aprepitant compared to a single oral dose of 40 mg aprepitant, which was not considered clinically meaningful.
Distribution
Aprepitant was greater than 99% bound to plasma proteins. The mean volume of distribution following APONVIE administration was approximately 72 L in healthy subjects.
Aprepitant crossed the blood-brain barrier in humans [see Mechanism Of Action].
Elimination
Metabolism
Aprepitant underwent extensive metabolism. In vitro studies using human liver microsomes indicated that aprepitant was metabolized primarily by CYP3A4 with minor metabolism by
CYP1A2 and CYP2C19. Metabolism was largely via oxidation at the morpholine ring and its side chains. No metabolism by CYP2D6, CYP2C9, or CYP2E1 was detected.
In healthy young adults, aprepitant accounted for approximately 24% of the radioactivity in plasma over 72 hours following a single oral 300 mg dose of [14C]-aprepitant, indicating a substantial presence of metabolites in the plasma. Seven metabolites of aprepitant, which were only weakly active, had been identified in human plasma.
Excretion
Aprepitant was eliminated primarily by metabolism; aprepitant was not renally excreted. The mean terminal half-life of aprepitant following administration of APONIVE was 12 hours. The mean plasma clearance of aprepitant was 4.4 L/h.
Specific Populations
Geriatric Patients
Following oral administration of a single 125 mg dose of aprepitant on Day 1 and 80 mg once daily on Days 2 through 5, the AUC0-24hr of aprepitant was 21% higher on Day 1 and 36% higher on Day 5 in healthy elderly subjects (65 years and older) relative to younger adult subject. The Cmax was 10% higher on Day 1 and 24% higher on Day 5 in healthy elderly subjects relative to younger adult subjects. These differences are not considered clinically meaningful [see Use In Specific Populations].
Male And Female Patients
Following oral administration of a single dose of aprepitant ranging from 40 mg to 375 mg, the AUC0-24hr and Cmax are 9% and 17% higher in females as compared with males. The half-life of aprepitant was approximately 25% lower in females as compared with males. These differences are not considered clinically meaningful.
Racial Or Ethnic Groups
Following oral administration of a single dose of aprepitant, ranging from 40 mg to 375 mg, the AUC0-24hr and Cmax were approximately 27% and 19% higher in Hispanics as compared with Caucasians. The AUC0-24hr and Cmax were 74% and 47% higher in Asians as compared to Caucasians. There was no difference in AUC0-24hr or Cmax between Caucasians and Blacks. These differences are not considered clinically meaningful.
Patients With Renal Impairment
A single 240 mg oral dose of aprepitant was administered to patients with severe renal impairment (creatinine clearance less than 30 mL/min/1.73 m2 as measured by 24-hour urinary creatinine clearance) and to patients with end stage renal disease (ESRD) requiring hemodialysis. In patients with severe renal impairment, the AUC0-∞ of total aprepitant (unbound and protein bound) decreased by 21% and Cmax decreased by 32%, relative to healthy subjects (creatinine clearance greater than 80 mL/min estimated by Cockcroft-Gault method). In patients with ESRD undergoing hemodialysis, the AUC0-∞ of total aprepitant decreased by 42% and Cmax decreased by 32%. Due to modest decreases in protein binding of aprepitant in patients with renal disease, the AUC of pharmacologically active unbound drug was not significantly affected in patients with renal impairment compared with healthy subjects. Hemodialysis conducted 4 or 48 hours after dosing had no significant effect on the pharmacokinetics of aprepitant; less than 0.2% of the dose was recovered in the dialysate.
No clinically meaningful changes in the pharmacokinetics of aprepitant are expected in patients with any degree of renal impairment following administration of a single dose of APONVIE 32 mg as an intravenous injection.
Patients With Hepatic Impairment
Following administration of a single 125 mg oral dose of aprepitant on Day 1 and 80 mg once daily on Days 2 and 3 to patients with mild hepatic impairment (Child-Pugh score 5 to 6), the AUC0-24hr of aprepitant was 11% lower on Day 1 and 36% lower on Day 3, as compared with healthy subjects given the same regimen. In patients with moderate hepatic impairment (Child Pugh score 7 to 9), the AUC0-24hr of aprepitant was 10% higher on Day 1 and 18% higher on Day 3, as compared with healthy subjects given the same regimen. These differences in AUC0-24hr are not considered clinically meaningful.
No clinically meaningful changes in the pharmacokinetics of aprepitant are expected in patients with mild or moderate hepatic impairment following administration of a single dose of APONVIE 32 mg as an intravenous injection. There are no clinical or pharmacokinetic data in patients with severe hepatic impairment (Child-Pugh score greater than 9).
Body Mass Index (BMI)
For every 5 kg/m2 increase in BMI, AUC0-24hr and Cmax of aprepitant decrease by 9% and 10%. BMI of subjects in the analysis ranged from 18 kg/m2 to 36 kg/m2. This change is not considered clinically meaningful.
Drug Interactions Studies
Aprepitant is a substrate, a weak-to-moderate (dose-dependent) inhibitor, and an inducer of CYP3A4. Aprepitant is also an inducer of CYP2C9. Aprepitant is unlikely to interact with drugs that are substrates for the P-glycoprotein transporter.
Aprepitant acts as a weak inhibitor of CYP3A4 when administered as a single intravenous 32 mg dose of APONVIE.
Effects Of Aprepitant On The Pharmacokinetics Of Other Drugs
CYP3A4 Substrates
Midazolam: Oral aprepitant 40 mg administered as a single oral dose on Day 1 increased the AUC of oral midazolam 2 mg by approximately 1.2-fold on Day 1. This effect was not considered clinically meaningful.
Corticosteroids
Dexamethasone: A single dose of oral aprepitant 40 mg when coadministered with a single dose of dexamethasone 20 mg, increased the AUC of dexamethasone by 1.45-fold, which is not considered clinically meaningful.
Methylprednisolone: Although the concomitant administration of methylprednisolone with the single 40 mg dose of oral aprepitant has not been studied, a single 40 mg dose of oral aprepitant produces a weak inhibition of CYP3A4 (based on midazolam interaction study) and it is not expected to alter the plasma concentrations of methylprednisolone to a clinically meaningful degree.
CYP2C9 substrates
Warfarin: A single 125 mg dose of oral aprepitant was administered on Day 1 and 80 mg/day on Days 2 and 3 to subjects who were stabilized on chronic warfarin therapy. Although there was no effect of oral aprepitant on the plasma AUC of R(+) or S(-) warfarin determined on Day 3, there was a 34% decrease in S(-) warfarin trough concentration accompanied by a 14% decrease in the prothrombin time (reported as International Normalized Ratio or INR) 5 days after completion of dosing with oral aprepitant [see DRUG INTERACTIONS].
Tolbutamide: Oral aprepitant, when given as a 40 mg single dose on Day 1, decreased the AUC of tolbutamide by 8% on Day 2, 16% on Day 4, 15% on Day 8, and 10% on Day 15, when a single dose of tolbutamide 500 mg was administered prior to the administration of oral aprepitant 40 mg and on Days 2, 4, 8, and 15. This effect was not considered clinically meaningful.
Other Drugs
Oral contraceptives: When a daily dosage of an oral contraceptive containing ethinyl estradiol and norgestimate was administered on Days 1 through 21, and oral aprepitant 40 mg was given on Day 8, the AUC of ethinyl estradiol decreased by 4% and by 29% on Day 8 and Day 12, respectively, while the AUC of norelgestromin increased by 18% on Day 8 and decreased by 10% on Day 12. In addition, the trough concentrations of ethinyl estradiol and norelgestromin on Days 8 through 21 were generally lower following coadministration of the oral contraceptive with oral aprepitant 40 mg on Day 8 compared to the trough levels following administration of the oral contraceptive alone [see DRUG INTERACTIONS].
P-glycoprotein substrates: Aprepitant is unlikely to interact with drugs that are substrates for the P-glycoprotein transporter, as demonstrated by the lack of interaction of oral aprepitant with digoxin in a clinical drug interaction study.
5-HT3 antagonists: In clinical drug interaction studies, aprepitant did not have clinically important effects on the pharmacokinetics of ondansetron, granisetron, or hydrodolasetron (the active metabolite of dolasetron).
Effect Of Other Drugs On The Pharmacokinetics Of Aprepitant
Rifampin
When a single 375 mg dose of oral aprepitant was administered on Day 9 of a 14-day regimen of 600 mg/day of rifampin, a strong CYP3A4 inducer, the AUC of aprepitant decreased approximately 11-fold and the mean terminal half-life decreased approximately 3-fold [see DRUG INTERACTIONS].
Ketoconazole
When a single 125 mg dose of oral aprepitant was administered on Day 5 of a 10-day regimen of 400 mg/day of ketoconazole, a strong CYP3A4 inhibitor, the AUC of aprepitant increased approximately 5-fold and the mean terminal half-life of aprepitant increased approximately 3-fold [see DRUG INTERACTIONS].
Diltiazem
In a study in 10 subjects with mild to moderate hypertension, administration of 100 mg of fosaprepitant, a prodrug of aprepitant, as an intravenous infusion with 120 mg of diltiazem, a moderate CYP3A4 inhibitor administered three times daily, resulted in a 1.5-fold increase in the aprepitant AUC and a 1.4-fold increase in the diltiazem AUC. This effect was not considered clinically meaningful.
When fosaprepitant was administered with diltiazem, the mean maximum decrease in diastolic blood pressure was greater than that observed with diltiazem alone (24.3 ± 10.2 mm Hg with fosaprepitant versus 15.6 ± 4.1 mm Hg without fosaprepitant). The mean maximum decrease in systolic blood pressure was also greater after co-administration of diltiazem with fosaprepitant than administration of diltiazem alone (29.5 ± 7.9 mm Hg with fosaprepitant versus 23.8 ± 4.8 mm Hg without fosaprepitant). Co-administration of fosaprepitant and diltiazem, however, did not result in any additional clinically meaningful changes in heart rate or PR interval, beyond those changes observed with diltiazem alone.
Paroxetine
Coadministration of once daily doses of oral aprepitant 85 mg or 170 mg, with paroxetine 20 mg once daily, resulted in a decrease in AUC by approximately 25% and Cmax by approximately 20% of both aprepitant and paroxetine. This effect was not considered clinically meaningful.
Clinical Studies
The safety and efficacy of APONVIE have been established based on adequate and wellcontrolled studies of a single-dose of oral aprepitant in adults. Below is a description of the results of these adequate and well-controlled studies of oral aprepitant for the prevention of PONV.
In two multicenter, randomized, double-blind, active comparator-controlled, parallel-group clinical studies (Studies 1 and 2), oral aprepitant was compared with ondansetron for the prevention of postoperative nausea and vomiting in 1658 patients undergoing open abdominal surgery. These two studies were of similar design; however, they differed in terms of study hypothesis, efficacy analyses, and geographic location. Study 1 was a multinational study including the U.S., whereas, Study 2 was conducted entirely in the U.S.
In the two studies, patients were randomized to receive 40 mg oral aprepitant, 125 mg oral aprepitant, or 4 mg intravenous ondansetron as a single dose. Aprepitant was given orally with 50 mL of water 1 to 3 hours before anesthesia. Ondansetron was given intravenously immediately before induction of anesthesia. A comparison between the oral aprepitant 125 mg dose did not demonstrate any additional clinical benefit over the oral 40 mg dose.
Of the 564 patients who received 40 mg oral aprepitant, 92% were women and 8% were men; of these, 58% were White, 13% Hispanic American, 7% Multi-Racial, 14% Black, 6% Asian, and 2% Other. The age of patients treated with 40 mg oral aprepitant ranged from 19 to 84 years, with a mean age of 46.1 years. 46 patients were 65 years or older, with 13 patients being 75 years or older.
The antiemetic activity of oral aprepitant was evaluated during the 0 to 48 hour period following the end of surgery.
Efficacy measures in Study 1 included:
- no emesis (defined as no emetic episodes regardless of use of rescue therapy) in the 0 to 24 hours following the end of surgery (primary)
- complete response (defined as no emetic episodes and no use of rescue therapy) in the 0 to 24 hours following the end of surgery (primary)
- no emesis (defined as no emetic episodes regardless of use of rescue therapy) in the 0 to 48 hours following the end of surgery (secondary)
- time to first use of rescue medication in the 0 to 24 hours following the end of surgery (exploratory)
- time to first emesis in the 0 to 48 hours following the end of surgery (exploratory)
A closed testing procedure was applied to control the type I error for the primary endpoints.
The results of the primary and secondary endpoints for 40 mg oral aprepitant and 4 mg ondansetron are described in Table 4.
Table 4: Response Rates for Select Efficacy Endpoints (Modified-Intention-to-Treat Population) – Study 1
| Treatment |
n/N (%) |
Oral Aprepitant
vs.
Ondansetron |
| Differencea |
Odds
Ratiob |
Analysis |
| PRIMARY ENDPOINTS |
No Vomiting 0 to 24 hours (Superiority)
(no emetic episodes) |
| Oral aprepitant 40 mg |
246/293 (84.0) |
12.6% |
2.1 |
P<0.001c |
| Ondansetron |
200/280 (71.4) |
|
|
|
Complete Response (Non-inferiority: If LBd >0.65)
(no emesis and no rescue therapy, 0 to 24 hours) |
| Oral aprepitant 40 mg |
187/293 (63.8) |
8.8% |
1.4 |
LB=1.02 |
| Ondansetron |
154/280 (55.0) |
|
|
|
Complete Response (Superiority: If LB >1.0)
(no emesis and no rescue therapy, 0 to 24 hours) |
| Oral aprepitant 40 mg |
187/293 (63.8) |
8.8% |
1.4 |
LB=1.02d |
| Ondansetron |
154/280 (55.0) |
|
|
|
| SECONDARY ENDPOINT |
| No Vomiting 0 to 48 hours (Superiority) (no emetic episodes) |
| Oral aprepitant 40 mg |
238/292 (81.5) |
15.2% |
2.3 |
P<0.001e |
| Ondansetron |
185/279 (66.3) |
|
|
|
n/N = Number of responders/number of patients in analysis.
a Difference (%): oral aprepitant 40 mg minus ondansetron.
b Estimated odds ratio for oral aprepitant versus ondansetron. A value of >1 favors aprepitant over ondansetron.
c P-value of two-sided test <0.05.
d LB = lower bound of 1-sided 97.5% confidence interval for the odds ratio.
e Based on the prespecified fixed sequence multiplicity strategy, oral aprepitant 40 mg was not superior to ondansetron. |
In Study 1, the use of oral aprepitant did not affect the time to first use of rescue medication when compared to ondansetron. However, compared to the ondansetron group, use of oral aprepitant delayed the time to first vomiting, as depicted in Figure 1.
Figure 1: Percent of Patients Who Remain Emesis Free During the 48 Hours Following Eng of Surgery in Study 1
Efficacy measures in Study 2 included:
- complete response (defined as no emetic episode and no use of rescue theraphy) in the 0 to 24 hours following the end of surgery (primary)
- no emesis (defined as no emetic episodes regardless of use rescue theraphy) in the 0 to 24 following the end of surgery (secondary)
- no use of rescue theraphy in the 0 to 24 hours following the end of surgery (secondary)
- no emesis (defined as no emetic episode regarless of use of rescue theraphy) in the 0 to 48 hours following the end of surgery (secondary)
Study 2 failed to satisfy its primary hypothesis that oral aprepitant is superior to ondansetron in the prevention of PONV as measured by the propotion of patients with complete response in the 24 hours following end of surgery.
The study demonstrated that 40 mg oral aprepitant had a clinically meaningful effect with respect to the secondary endpoint “no vomiting” during the first 24 hours after surgery and was associated with a 16% improvement over ondansetron for the no vomiting endpont (Table 5).
Table 5: Response Rates for Select Efficacy Endpoints (Modified-Intention-to-Treat Population) – Study 2
| Treatment |
n/N (%) |
Oral Aprepitant vs.
Ondansetron |
| Differencea |
Odds
Ratiob |
Analysis |
| PRIMARY ENDPOINT |
Complete Response
(no emesis and no rescue therapy, 0 to 24 hours) |
| Oral aprepitant 40 mg |
111/248 (44.8) |
2.5% |
1.1 |
0.61 |
| Ondansetron |
104/246 (42.3) |
|
|
|
| SECONDARY ENDPOINTS |
No Vomiting
(no emetic episodes, 0 to 24 hours) |
| Oral aprepitant 40 mg |
223/248 (89.9) |
16.3% |
3.2 |
<0.001c |
| Ondansetron |
181/246 (73.6) |
|
|
|
No Use of Rescue Medication
(for established emesis or nausea, 0 to 24 hours) |
| Oral aprepitant 40 mg |
112/248 (45.2) |
-0.7% |
1.0 |
0.83 |
| Ondansetron |
113/246 (45.9) |
|
|
|
No Vomiting 0 to 48 hours (Superiority)
(no emetic episodes, 0 to 48 hours) |
| Oral aprepitant 40 mg |
209/247 (84.6) |
17.7% |
2.7 |
<0.001c |
| Ondansetron |
164/245 (66.9) |
|
|
|
n/N = Number of responders/number of patients in analysis.
a Difference (%): oral aprepitant 40 mg minus ondansetron.
b Estimated odds ratio: oral aprepitant 40 mg versus ondansetron.
c Not statistically significant after prespecified multiplicity adjustment. |